1. Field of the Invention
The present invention relates to a solid-state imaging device including photoelectric converting regions which are arranged on a semiconductor substrate.
2. Description of the Related Art
In the related art, a digital camera is known in which the dynamic range is widened by using a solid-state imaging device having the following configuration (see JP-A-10-74926). The solid-state imaging device includes: first photoelectric converting regions which are arranged on a semiconductor substrate in a row direction and a column direction that is perpendicular to the row direction; and microlenses which are disposed on the first photoelectric converting regions, respectively. Each of second photoelectric converting regions is placed between the microlenses. Image signals from the first photoelectric converting regions and those from the second photoelectric converting regions are combined with each other.
In such a solid-state imaging device, plural photoelectric converting regions are arranged on a semiconductor substrate in a high density, and hence distances between microlenses respectively corresponding to the photoelectric converting regions are very short. In the technique disclosed in JP-A-10-74926, the second photoelectric converting regions are disposed between the microlenses. As described above, the distances between the microlenses are very short. When the second photoelectric converting regions are not provided with an opening of an improved shape, therefore, shading is caused by the microlenses. Hereinafter, the reason of this phenomenon will be described.
FIG. 6 is a view schematically showing a section of the solid-state imaging device disclosed in JP-A-10-74926.
As shown in FIG. 6A, light a which vertically enters from the upper side of the related-art solid-state imaging device is incident on a microlens 601, and then passed through an opening face 602 to be collected on a first photodiode (PD) 603. Charges accumulated in the PD are transferred through a first vertical transfer section 604. Furthermore, light a is passed through an opening face 605 to be incident on a second PD 606 placed between microlenses 601, and charges accumulated in the PD are transferred through a second vertical transfer section 607.
As shown in FIG. 6B, light b which enters from the upper side of the solid-state imaging device obliquely with the arrangement direction of two microlenses 601 that are placed across the second PD 606 is incident on one of the microlenses 601, and then passed through the opening face 602 to be collected on the first PD 603. Charges accumulated in the PD are transferred through the first vertical transfer section 604. Also, light b is passed through the opening face 605 to be incident on the second PD 606. However, part (the arrow indicated by the broken line) of the light b cannot be passed through the opening face 605. Also light c which enters in a direction that is symmetrical to the light b operates in the same manner. By contrast, most of light which enters in a direction (a direction perpendicular to the direction indicated by the arrow X in the figure) along which the second PD 606 is not interposed between the microlenses 601 is incident on the second PD 606 because there is no obstacle such as microlenses.
As described above, in the case where the PD is placed in the narrow region between the two microlenses 601, a large portion of the PD hides behind the microlenses 601 with respect to light b, c which enters obliquely in the direction along which the second PD 606 is interposed between the microlenses 601. Therefore, most of such light cannot be passed through the opening face 605. By contrast, most of light which enters in a direction along which the second PD 606 is not interposed between the microlenses 601 is incident on the second PD 606. In an image obtained from the second PD 606, consequently, brightness in the direction (a direction perpendicular to the direction X) along which the second PD 606 is not interposed between the microlenses 601 is higher, and that in the arrangement direction (the direction X) of the two microlenses 601 between which the second PD 606 is interposed is lower, thereby causing shading. This shading is not shading which is caused in a peripheral portion of the solid-state imaging device of FIG. 6 by an optical system of the digital camera on which the solid-state imaging device is mounted, but special shading which is caused by the microlenses 601.
JP-A-10-74926 teaches nothing about a configuration for reducing such special shading, such as a specific shape of the opening for the second PD 606.